The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
The cables of suspension bridges and cable stayed bridges as well as similar lengthy tubular metal articles utilized outdoors are frequently subjected to severe environmental and climatic conditions. Even if conditions are relatively mild, the initial investment and the expected, extended service life demand that all practical efforts be undertaken to maintain the structure. Typically, therefore, such cables and articles are painted or otherwise coated to minimize rusting or other deterioration from such exposure. Although protected with suitable weather resistant paint or other coatings, periodic repainting or recoating of such cables and articles is invariably necessary. Such activity is costly and time consuming because of the relative inaccessibility of such cables. The cost and time involved are further increased because proper maintenance practice generally dictates removal of the previous paint or coating. Such removal typically raises environmental issues.
An alternative to such repeated repainting or recoating involves permanent application of a spiral or helical wrap of a Neoprene or similar polychloroprene band or strip about the cable or article. This approach to cable protection was not without drawbacks, however. First of all, the Neoprene could not be colored and thus, after application, if it was desired that the cable covering match the rest of the structure, it would still require painting. Second of all, it was necessary to seal adjacent layers of the wrap to one another with a solvent. This again was a labor intensive undertaking.
An improvement to this approach comprehends the application of a spiral wrap of Hypalon® to the cable or article. Hypalon is a registered trademark of the E.I. DuPont de Nemours Company for its brand of chlorosulfonated polyethylene. This material can be sealed to itself with the application of sufficient heat and thus eliminates the above-noted solvent sealing step. The use of a heat sealed spiral wrap of a band or strip of Hypalon® is described in detail in co-owned U.S. Pat. No. 5,390,386. Study of the subject patent reveals that proper sealing of the adjacent wraps or layers of Hypalon® is dependent upon sufficient and uniform application of heat to the exterior of the wrapped cable.
Because the various strands and cables that constitute the suspension cable do not assemble and nest uniformly, the outer surface of the suspension cable is irregular. Such an irregular surface, of course, is generally duplicated by the spiral wrapped band or strip, rendering uniform heat application difficult: protruding regions are in intimate contact with a heating device and may receive excessive heat while recessed regions may not contact the heating device and thus receive little heat. The present invention is directed to ensuring the sufficient and uniform application of heat to the exterior of the wrapped cable to provide the optimum protection to the cable and therefore its longest life with reduced maintenance expense.